Varicella-zoster virus infection triggers formation of an interleukin-1β (IL-1β)-processing inflammasome complex

Advances in the mechanism of inflammasomes activation in herpes virus infection

Herpesviruses, prevalent DNA viruses with a double-stranded structure, establish enduring infections and play a part in various diseases. Despite their deployment of multiple tactics to evade the immune system, both localized and systemic inflammatory responses are triggered by the innate immune system's recognition of them. Recent progress has offered more profound understandings of the mechanisms behind the activation of the innate immune system by herpesviruses, specifically through inflammatory signaling. This process encompasses the initiation of an intracellular nucleoprotein complex, the inflammasome associated with inflammation.Following activation, proinflammatory cytokines such as IL-1β and IL-18 are released by the inflammasome, concurrently instigating a programmed pathway for cell death. Despite the structural resemblances between herpesviruses, the distinctive methods of inflammatory activation and the ensuing outcomes in diseases linked to the virus exhibit variations.The objective of this review is to emphasize both the similarities and differences in the mechanisms of inflammatory activation among herpesviruses, elucidating their significance in diseases resulting from these viral infections.Additionally, it identifies areas requiring further research to comprehensively grasp the impact of this crucial innate immune signaling pathway on the pathogenesis of these prevalent viruses.

Simian varicella virus infection and reactivation in rhesus macaques trigger cytokine and Aβ40/42 alterations in serum and cerebrospinal fluid

Simian varicella virus (SVV) produces peripheral inflammatory responses during varicella (primary infection) and zoster (reactivation) in rhesus macaques (RM). However, it is unclear if peripheral measures are accurate proxies for central nervous system (CNS) responses. Thus, we analyzed cytokine and Aβ42/Aβ40 changes in paired serum and cerebrospinal fluid (CSF) during the course of infection. During varicella and zoster, every RM had variable changes in serum and CSF cytokine and Aβ42/Aβ40 levels compared to pre-inoculation levels. Overall, peripheral infection appears to affect CNS cytokine and Aβ42/Aβ40 levels independent of serum responses, suggesting that peripheral disease may contribute to CNS disease.

New insights into nucleic acid sensor AIM2: The potential benefit in targeted therapy for cancer

The AIM2 inflammasome represents a multifaceted oligomeric protein complex within the innate immune system, with the capacity to perceive double-stranded DNA (dsDNA) and engage in diverse physiological reactions and disease contexts, including cancer. While originally conceived as a discerning DNA sensor, AIM2 has demonstrated its capability to discern various nucleic acid variations, encompassing RNA and DNA-RNA hybrids. Through its interaction with nucleic acids, AIM2 orchestrates the assembly of a complex involving multiple proteins, aptly named the AIM2 inflammasome, which facilitates the enzymatic cleavage of proinflammatory cytokines, namely pro-IL-1β and pro-IL-18. This process, in turn, underpins its pivotal biological role. In this review, we provide a systematic summary and discussion of the latest advancements in AIM2 sensing various types of nucleic acids. Additionally, we discuss the modulation of AIM2 activation, which can cause cell death, including pyroptosis, apoptosis, and autophagic cell death. Finally, we fully illustrate the evidence for the dual role of AIM2 in different cancer types, including both anti-tumorigenic and pro-tumorigenic functions. Considering the above information, we uncover the therapeutic promise of modulating the AIM2 inflammasome in cancer treatment.

Varicella zoster virus glycoprotein E facilitates PINK1/Parkin-mediated mitophagy to evade STING and MAVS-mediated antiviral innate immunity

Viruses have evolved to control mitochondrial quality and content to facilitate viral replication. Mitophagy is a selective autophagy, in which the damaged or unnecessary mitochondria are removed, and thus considered an essential mechanism for mitochondrial quality control. Although mitophagy manipulation by several RNA viruses has recently been reported, the effect of mitophagy regulation by varicella zoster virus (VZV) remains to be fully determined. In this study, we showed that dynamin-related protein-1 (DRP1)-mediated mitochondrial fission and subsequent PINK1/Parkin-dependent mitophagy were triggered during VZV infection, facilitating VZV replication. In addition, VZV glycoprotein E (gE) promoted PINK1/Parkin-mediated mitophagy by interacting with LC3 and upregulating mitochondrial reactive oxygen species. Importantly, VZV gE inhibited MAVS oligomerization and STING translocation to disrupt MAVS- and STING-mediated interferon (IFN) responses, and PINK1/Parkin-mediated mitophagy was required for VZV gE-mediated inhibition of IFN production. Similarly, carbonyl cyanide m-chlorophenyl hydrazone (CCCP)-mediated mitophagy induction led to increased VZV replication but attenuated IFN production in a three-dimensional human skin organ culture model. Our results provide new insights into the immune evasion mechanism of VZV gE via PINK1/Parkin-dependent mitophagy.

Simian Varicella Virus Infection and Reactivation in Rhesus Macaques Trigger Cytokine and Aβ40/42 Alterations in Serum and Cerebrospinal Fluid

Simian varicella virus (SVV) produces peripheral inflammatory responses during varicella (primary infection) and zoster (reactivation) in rhesus macaques (RM). However, it is unclear if peripheral measures are accurate proxies for central nervous system (CNS) responses. Thus, we analyzed cytokine and Aβ42/Aβ40 changes in paired serum and cerebrospinal fluid (CSF) during the course of infection. During varicella and zoster, every RM had variable changes in serum and CSF cytokine and Aβ42/Aβ40 levels compared to pre-inoculation levels. Overall, peripheral infection appears to affect CNS cytokine and Aβ42/Aβ40 levels independent of serum responses, suggesting that peripheral disease may contribute to CNS disease.

Pseudorabies virus infection activates the NLRP3 and IFI16 inflammasomes to trigger pyroptosis

Pseudorabies virus (PRV) preferably invades neural tissue and various organs, whereupon may result in multisystemic lesions. Pyroptosis mediated by proteolytic cleavage of gasdermin D (GSDMD) by inflammatory caspases (caspase-1/4/5/11), is closely associated with the activation of inflammasomes, a multiprotein proinflammatory complex. However, further studies on the mechanisms regarding PRV-induced pyroptosis in its natural host are required. Herein, it is demonstrated that PRV infection triggered GSDMD- not GSDME-mediated pyroptosis in porcine alveolar macrophage cells, resulting in increased secretion of IL-1β and LDH. During this process, caspase-1 was activated and participated in the cleaving of GSDMD. Interestingly, we found that the viral replication process or protein production is required to induce pyroptotic cell death. Also, our findings showed that PRV triggered NLRP3 inflammasome activation, which was associated with the production of reactive oxygen species (ROS) and potassium efflux. In addition to the NLRP3 inflammasome, the IFI16 inflammasome was also activated. Importantly, the NLRP3- and IFI16- inflammasomes were both involved in pyroptosis during PRV infection. Finally, we observed that the cleaved GSDMD, activated caspase-1, increased IFI16 levels, and elevated NLRP3 protein in PRV-infected tissues (brain and lung), supporting the occurrence of pyroptosis and the activation of NLRP3- and IFI16- inflammasome in PRV-infected pigs. This research advances our understanding of the PRV-mediated inflammatory response and cell death pathways, providing a deeper knowledge of effective treatments for pseudorabies.

Lack of strong innate immune reactivity renders macrophages alone unable to control productive Varicella-Zoster Virus infection in an isogenic human iPSC-derived neuronal co-culture model

With Varicella-Zoster Virus (VZV) being an exclusive human pathogen, human induced pluripotent stem cell (hiPSC)-derived neural cell culture models are an emerging tool to investigate VZV neuro-immune interactions. Using a compartmentalized hiPSC-derived neuronal model allowing axonal VZV infection, we previously demonstrated that paracrine interferon (IFN)-α2 signalling is required to activate a broad spectrum of interferon-stimulated genes able to counteract a productive VZV infection in hiPSC-neurons. In this new study, we now investigated whether innate immune signalling by VZV-challenged macrophages was able to orchestrate an antiviral immune response in VZV-infected hiPSC-neurons. In order to establish an isogenic hiPSC-neuron/hiPSC-macrophage co-culture model, hiPSC-macrophages were generated and characterised for phenotype, gene expression, cytokine production and phagocytic capacity. Even though immunological competence of hiPSC-macrophages was shown following stimulation with the poly(dA:dT) or treatment with IFN-α2, hiPSC-macrophages in co-culture with VZV-infected hiPSC-neurons were unable to mount an antiviral immune response capable of suppressing a productive neuronal VZV infection. Subsequently, a comprehensive RNA-Seq analysis confirmed the lack of strong immune responsiveness by hiPSC-neurons and hiPSC-macrophages upon, respectively, VZV infection or challenge. This may suggest the need of other cell types, like T-cells or other innate immune cells, to (co-)orchestrate an efficient antiviral immune response against VZV-infected neurons.

Varicella Zoster Virus infects mucosal associated Invariant T cells

Introduction

Mucosal Associated Invariant T (MAIT) cells are innate-like T cells that respond to conserved pathogen-derived vitamin B metabolites presented by the MHC class I related-1 molecule (MR1) antigen presentation pathway. Whilst viruses do not synthesize these metabolites, we have reported that varicella zoster virus (VZV) profoundly suppresses MR1 expression, implicating this virus in manipulation of the MR1:MAIT cell axis. During primary infection, the lymphotropism of VZV is likely to be instrumental in hematogenous dissemination of virus to gain access to cutaneous sites where it clinically manifests as varicella (chickenpox). However, MAIT cells, which are found in the blood and at mucosal and other organ sites, have yet to be examined in the context of VZV infection. The goal of this study was to examine any direct impact of VZV on MAIT cells.

Methods

Using flow cytometry, we interrogated whether primary blood derived MAIT cells are permissive to infection by VZV whilst further analysing differential levels of infection between various MAIT cell subpopulations. Changes in cell surface extravasation, skin homing, activation and proliferation markers after VZV infection of MAIT cells was also assessed via flow cytometry. Finally the capacity of MAIT cells to transfer infectious virus was tested through an infectious center assay and imaged via fluorescence microscopy.

Results

We identify primary blood-derived MAIT cells as being permissive to VZV infection. A consequence of VZV infection of MAIT cells was their capacity to transfer infectious virus to other permissive cells, consistent with MAIT cells supporting productive infection. When subgrouping MAIT cells by their co- expression of a variety cell surface markers, there was a higher proportion of VZV infected MAIT cells co-expressing CD4+ and CD4+/CD8+ MAIT cells compared to the more phenotypically dominant CD8+ MAIT cells, whereas infection was not associated with differences in co-expression of CD56 (MAIT cell subset with enhanced responsiveness to innate cytokine stimulation), CD27 (co-stimulatory) or PD-1 (immune checkpoint). Infected MAIT cells retained high expression of CCR2, CCR5, CCR6, CLA and CCR4, indicating a potentially intact capacity for transendothelial migration, extravasation and trafficking to skin sites. Infected MAIT cells also displayed increased expression of CD69 (early activation) and CD71 (proliferation) markers.

Discussion

These data identify MAIT cells as being permissive to VZV infection and identify impacts of such infection on co- expressed functional markers.

A simple transwell-based infection system for obtaining pure populations of VZV-infected cells

Varicella-Zoster virus (VZV) is a human herpesvirus and causes chickenpox and shingles. Research into its molecular virology has been hampered by a lack of methods for generation of high-titre, cell-free infectious virus preparations. VZV propagation and infection in vitro are therefore commonly achieved by co-culture of uninfected 'target' cells with infected 'inoculum' cells. A major drawback of this approach is that it results in mixed cell populations after infection. To overcome this limitation we developed a transwell-based VZV infection system. Infected inoculum cells and uninfected target cells are spatially separated by a transwell membrane. While cell-cell contact and VZV spread can occur through membrane pores, the two cell populations do not mix. This simple protocol requires no special instrumentation or reagents. We successfully used this system for infection of a range of target cells and obtained pure populations for downstream analyses such as flow cytometry and RT-qPCR. In sum, we developed a broadly applicable approach to study the molecular and cellular biology as well as host-pathogen interactions of VZV.

The Contrasting Seasonality Patterns of Some Cancer-Types and Herpes Zoster Can Be Explained by a Binary Classification of Immunological Reactions

A binary classification of the pathogenic immune reactions as anti-inflammatory high-Treg reactions or pro-inflammatory low-Treg reactions explains both the relatively low incidence rate of several types of cancer, and the relatively high incidence rate of herpes zoster cases diagnosed in the summer compared to cases diagnosed in the winter (in regions with temperate climate). This binary model also elucidates the longer survival of cancer patients diagnosed during the summer compared to these diagnosed in the winter. The three key elements of this explanation are: (a) the effect of sunlight on Treg production; (b) the evolvement of cancer from a low-Treg condition at early stage, to a high-Treg condition at advanced stage, and (c) the evolvement of herpes zoster from a high-Treg condition at pre-exudative stage to a low-Treg condition at acute exudative stage. A significant proportion of indolent tumors at the time of diagnosis (>20%) is a prerequisite for a beneficial effect of sunlight on cancer incidence rate and prognosis. This prerequisite restricts the beneficial effect of diagnosis during summer to certain types of cancer. Clinical implication: the prognosis of early stage tumors may be improved by a course of corticosteroid (or other immunosuppressant) treatment.

Mollaret Meningitis Caused by Varicella-Zoster Virus: A Case Report

Mollaret meningitis is a recurrent aseptic meningitis mostly caused by herpes simplex virus type 2. Other causes of the disease rarely exist, and its pathology is not well understood. Herein, we present a 57-year-old man who had been admitted to our hospital eight times with recurrent aseptic meningitis. Although the deoxyribonucleic acid (DNA) of varicella-zoster virus (VZV) was not detected in the cerebrospinal fluid (CSF), his genetic analysis, measurement of anti-VZV immunoglobulin-G (IgG) in the CSF, the VZV IgG index, IgG in the serum, and interleukin-1 beta in the CSF revealed that the Mollaret meningitis had been caused by the VZV. This case demonstrates that Mollaret meningitis can be caused by the VZV when specific factors are associated with decreased immune response. This case is valuable in elucidating the pathophysiology of Mollaret meningitis.

Varicella-Zoster virus ORF9 is an antagonist of the DNA sensor cGAS

Varicella-Zoster virus (VZV) causes chickenpox and shingles. Although the infection is associated with severe morbidity in some individuals, molecular mechanisms that determine innate immune responses remain poorly defined. We found that the cGAS/STING DNA sensing pathway was required for type I interferon (IFN) induction during VZV infection and that recognition of VZV by cGAS restricted its replication. Screening of a VZV ORF expression library identified the essential VZV tegument protein ORF9 as a cGAS antagonist. Ectopically or virally expressed ORF9 bound to endogenous cGAS leading to reduced type I IFN responses to transfected DNA. Confocal microscopy revealed co-localisation of cGAS and ORF9. ORF9 and cGAS also interacted directly in a cell-free system and phase-separated together with DNA. Furthermore, ORF9 inhibited cGAMP production by cGAS. Taken together, these results reveal the importance of the cGAS/STING DNA sensing pathway for VZV recognition and identify a VZV immune antagonist that partially but directly interferes with DNA sensing via cGAS.

Herpesviruses and Inflammasomes: One Sensor Does Not Fit All

Herpesviruses are ubiquitous double-stranded DNA viruses that cause lifelong infections and are associated with a variety of diseases. While they have evolved multiple mechanisms to evade the immune system, they are all recognized by the innate immune system, which can lead to both localized and systemic inflammation. A more recently appreciated mechanism of herpesvirus innate immune activation is through inflammasome signaling. The inflammasome is an intracellular multiprotein complex that, when activated, leads to the release of proinflammatory cytokines, including IL-1β and IL-18, and activation of the inflammatory programed cell death pathway known as pyroptosis. Despite the herpesviruses sharing a similar structure, their mechanisms of inflammasome activation and the consequences of inflammasome activation in cases of virus-associated disease are not uniform. This review will highlight the similarities and differences among herpesviruses with regard to their mechanisms of inflammasome activation and impacts on diseases caused by herpesviruses. Furthermore, it will identify areas where additional studies are warranted to better understand the impact of this important innate immune signaling program on the pathogenesis of these common viruses.

Targeting Inflammasome Activation in COVID-19: Delivery of RNA Interference-Based Therapeutic Molecules

Mortality and morbidity associated with COVID-19 continue to be significantly high worldwide, owing to the absence of effective treatment strategies. The emergence of different variants of SARS-CoV-2 is also a considerable source of concern and has led to challenges in the development of better prevention and treatment strategies, including vaccines. Immune dysregulation due to pro-inflammatory mediators has worsened the situation in COVID-19 patients. Inflammasomes play a critical role in modulating pro-inflammatory cytokines in the pathogenesis of COVID-19 and their activation is associated with poor clinical outcomes. Numerous preclinical and clinical trials for COVID-19 treatment using different approaches are currently underway. Targeting different inflammasomes to reduce the cytokine storm, and its associated complications, in COVID-19 patients is a new area of research. Non-coding RNAs, targeting inflammasome activation, may serve as an effective treatment strategy. However, the efficacy of these therapeutic agents is highly dependent on the delivery system. MicroRNAs and long non-coding RNAs, in conjunction with an efficient delivery vehicle, present a potential strategy for regulating NLRP3 activity through various RNA interference (RNAi) mechanisms. In this regard, the use of nanomaterials and other vehicle types for the delivery of RNAi-based therapeutic molecules for COVID-19 may serve as a novel approach for enhancing drug efficacy. The present review briefly summarizes immune dysregulation and its consequences, the roles of different non-coding RNAs in regulating the NLRP3 inflammasome, distinct types of vectors for their delivery, and potential therapeutic targets of microRNA for treatment of COVID-19.

Cell Death in Coronavirus Infections: Uncovering Its Role during COVID-19

Cell death mechanisms are crucial to maintain an appropriate environment for the functionality of healthy cells. However, during viral infections, dysregulation of these processes can be present and can participate in the pathogenetic mechanisms of the disease. In this review, we describe some features of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and some immunopathogenic mechanisms characterizing the present coronavirus disease (COVID-19). Lymphopenia and monocytopenia are important contributors to COVID-19 immunopathogenesis. The fine mechanisms underlying these phenomena are still unknown, and several hypotheses have been raised, some of which assign a role to cell death as far as the reduction of specific types of immune cells is concerned. Thus, we discuss three major pathways such as apoptosis, necroptosis, and pyroptosis, and suggest that all of them likely occur simultaneously in COVID-19 patients. We describe that SARS-CoV-2 can have both a direct and an indirect role in inducing cell death. Indeed, on the one hand, cell death can be caused by the virus entry into cells, on the other, the excessive concentration of cytokines and chemokines, a process that is known as a COVID-19-related cytokine storm, exerts deleterious effects on circulating immune cells. However, the overall knowledge of these mechanisms is still scarce and further studies are needed to delineate new therapeutic strategies.

Host immune response in chronic hepatitis C infection: involvement of cytokines and inflammasomes

Chronic liver disease is a major health issue worldwide and chronic hepatitis C (CHC) is associated with an increased risk of cirrhosis and hepatocellular carcinoma (HCC). There is evidence that the hepatitis C virus (HCV) infection is correlated with immune senescence by way of immune activation and chronic inflammation, which lead to increased metabolic and cardiovascular risk, as well as progressive liver damage. Both the innate and adaptive immunity are firmly tied to the prognosis of an infection with HCV and its response to antiviral therapy. HCV is therefore associated with increased pro-inflammatory status, heightened production of cytokines, prolonged systemic inflammation, as well as increased morbidity and mortality, mainly due to the progression of hepatic fibrosis and HCC, but also secondary to cardiovascular diseases. Viral hepatic pathology is increasingly considered a disease that is no longer merely limited to the liver, but one with multiple metabolic consequences. Numerous in vitro studies, using experimental models of acute or chronic inflammation of the liver, has brought new information on immunopathological mechanisms resulting from viral infections and have highlighted the importance of involving complex structures, inflammasomes complex, in these mechanisms, in addition to the involvement of numerous proinflammatory cytokines. Beyond obtaining a sustained viral response and halting the aforementioned hepatic fibrosis, the current therapeutic “treat-to-target” strategies are presently focused on immune-mediated and metabolic disorders, to improve the quality of life and long-term prognosis of CHC patients.

ATP-dependent activation of NLRP3 inflammasome in primary murine macrophages infected by pseudorabies virus

Pseudorabies virus (PRV), an alphaherpesvirus, causes respiratory and reproductive diseases in pigs and severe nervous symptom in other susceptible hosts. Previous studies showed that PRV infection induced a systemic inflammatory response in mice, indicating that pro-inflammatory cytokines participated in viral neuropathy in mice. The pro-inflammatory cytokine IL-1β is a key mediator of the inflammatory response and plays an important role in host-response to pathogens. However, the secretion of IL-1β and its relationship with inflammasome activation during PRV infection remains poorly understood. In this study, we found that PRV infection caused significant secretion of several pro-inflammatory cytokines in macrophages and promoted IL-1β secretion in an ATP-dependent manner. Furthermore, the expression of IL-1β can be induced by only PRV infection and depended on NF-κB pathway activation, while the subsequent secretion of IL-1β was mediated by ATP-induced P2 × 7R activation, loss of intracellular K⁺, and the subsequent NLRP3 inflammasome activation. By using a mouse infection model, we also found that ATP exacerbated clinical signs and death of mice infected by PRV in a NLRP3-dependent manner. These results indicate that ATP facilitates activation of NLRP3 inflammasome and enhances the pathogenicity of PRV in mice during its acute infection.

Host Innate Immune Response and Viral Immune Evasion During Alphaherpesvirus Infection

Both the development of the mammalian innate immune system and the antagonistic strategies acquired by alphaherpesviruses to dismantle it have been shaped by co-evolving virus-host interactions over millions of years. Here, we review mechanisms employed by mammalian cells to detect pathogen molecules, such as viral glycoproteins and nucleic acids, and induce innate immune signaling upon infection with alphaherpesviruses. We further explore strategies acquired by these viruses to bypass immune detection and activation, thereby supporting virus replication and spread. Finally, we discuss the contributions of advanced 'omics' and microscopy methods to these discoveries in immune signaling and highlight emerging technologies that can help to further our understanding of the dynamic interplay between host innate immune responses and virus immune evasion.

[Pericarditis is inflammation of the pericardium, which rheumatologists should know]

Als Perikarditis wird eine Entzündung des Herzbeutels bezeichnet, die mit einem Perikarderguss oder einer entzündlichen Reaktion des Myokards (Perimyokarditis) einhergehen kann. Die Perikarditis kann im Rahmen von entzündlich rheumatischen Systemerkrankungen oder als eigenständige Erkrankung vorkommen. Rezidivierende Perikarditisepisoden ohne fassbare Ursache werden als idiopathische rekurrierende Perikarditis (IRP) bezeichnet, welche wesentliche Gemeinsamkeiten mit autoinflammatorischen Erkrankungen aufweist. Der Artikel gibt einen Überblick über die Häufigkeit des Auftretens einer Perikarditis bei rheumatologischen Erkrankungen. Weiterhin werden Klinik und Pathophysiologie der IRP diskutiert. Abschließend wird die Therapie der akuten und idiopathischen Perikarditis erläutert.

Ju Re Ba Du therapy for Postherpetic neuralgia: A protocol for systematic review and meta-analysis

INTRODUCTION

Postherpetic neuralgia (PHN) is one of the most common types of chronic neuropathic pain, which seriously affects quality of the life because of pain severity and poor response to the currently available treatments. Ju Re Ba Du therapy as a form of acupuncture therapy which is proved to be effective in RCTs and very suitable for patients, has been used in Postherpetic neuralgia in patients for a long time, therefore a systematic review is necessary to provide available evidence for further study.

METHODS AND ANALYSIS

The following databases will be searched from their inception to October 2020: Electronic database includes PubMed, Embase, Cochrane Library, Web of Science, Nature, Science online, VIP medicine information, and CNKI (China National Knowledge Infrastructure).

PRIMARY OUTCOME

pain intensity assessed on a visual analogue scale (VAS); Additional outcomes:Data will be extracted by two researchers independently, risk of bias of the meta-analysis will be evaluated based on the Cochrane Handbook for Systematic Reviews of Interventions. All data analysis will be conducted by data statistics software Review Manager V.5.3. and Stata V.12.0.

RESULTS

The results of this study will systematically evaluate the effectiveness and safety of Ju Re Ba Du therapy intervention for people with Postherpetic neuralgia.

CONCLUSION

The systematic review of this study will summarize the current published evidence of Ju Re Ba Du therapy for the treatment of Postherpetic neuralgia, which can further guide the promotion and application of it.

ETHICS AND DISSEMINATION

This study is a systematic review, the outcomes are based on the published evidence, so examination and agreement by the ethics committee are not required in this study. We intend to publish the study results in a journal or conference presentations.

OSF REGISTRATION NUMBER

September 29, 2020 osf.io/r6y9b. (https://osf.io/r6y9b).

Manipulation of the Innate Immune Response by Varicella Zoster Virus

Varicella zoster virus (VZV) is the causative agent of chickenpox (varicella) and shingles (herpes zoster). VZV and other members of the herpesvirus family are distinguished by their ability to establish a latent infection, with the potential to reactivate and spread virus to other susceptible individuals. This lifelong relationship continually subjects VZV to the host immune system and as such VZV has evolved a plethora of strategies to evade and manipulate the immune response. This review will focus on our current understanding of the innate anti-viral control mechanisms faced by VZV. We will also discuss the diverse array of strategies employed by VZV to regulate these innate immune responses and highlight new knowledge on the interactions between VZV and human innate immune cells.

Post-translational Control of Innate Immune Signaling Pathways by Herpesviruses

Herpesviruses constitute a large family of disease-causing DNA viruses. Each herpesvirus strain is capable of infecting particular organisms with a specific cell tropism. Upon infection, pattern recognition receptors (PRRs) recognize conserved viral features to trigger signaling cascades that culminate in the production of interferons and pro-inflammatory cytokines. To invoke a proper immune response while avoiding collateral tissue damage, signaling proteins involved in these cascades are tightly regulated by post-translational modifications (PTMs). Herpesviruses have developed strategies to subvert innate immune signaling pathways in order to ensure efficient viral replication and achieve persistent infection. The ability of these viruses to control the proteins involved in these signaling cascades post-translationally, either directly via virus-encoded enzymes or indirectly through the deregulation of cellular enzymes, has been widely reported. This ability provides herpesviruses with a powerful tool to shut off or restrict host antiviral and inflammatory responses. In this review, we highlight recent findings on the herpesvirus-mediated post-translational control along PRR-mediated signaling pathways.

NLRP3, NLRP12, and IFI16 Inflammasomes Induction and Caspase-1 Activation Triggered by Virulent HSV-1 Strains Are Associated With Severe Corneal Inflammatory Herpetic Disease

The crosstalk between the host's inflammasome system and the invading virulent/less-virulent viruses determines the outcome of the ensuing inflammatory response. An appropriate activation of inflammasomes triggers antiviral inflammatory responses that clear the virus and heal the inflamed tissue. However, an aberrant activation of inflammasomes can result in a harmful and overwhelming inflammation that could damage the infected tissue. The underlying host's immune mechanisms and the viral virulent factors that impact severe clinical inflammatory disease remain to be fully elucidated. In this study, we used herpes simplex virus type 1 (HSV-1), the causative agent of corneal inflammatory herpetic disease, as a model pathogen to determine: (i) Whether and how the virulence of a virus affects the type and the activation level of the inflammasomes; and (ii) How triggering specific inflammasomes translates into protective or damaging inflammatory response. We showed that, in contrast to the less-virulent HSV-1 strains (RE, F, KOS, and KOS63), corneal infection of B6 mice with the virulent HSV-1 strains (McKrae, 17 or KOS79): (i) Induced simultaneous expression of the NLRP3, NLRP12, and IFI16 inflammasomes; (ii) Increased production of the biologically active Caspase-1 and pro-inflammatory cytokines IL-1β and IL-18; (iii) Heightened recruitment into the inflamed cornea of CD45highLy6C+Ly6G-F4/80+CD11b+CD11c- inflammatory monocytes and CD45highCD11b+F4/80-Ly6GhiLy6Cmed neutrophils; and (iv) This intensified inflammatory response was associated with a severe corneal herpetic disease, irrespective of the level of virus replication in the cornea. Similarly, in vitro infection of human corneal epithelial cells and human monocytic THP-1 cells with the virulent HSV-1 strains triggered a synchronized early expression of NLRP3, NLRP12 and IFI16, 2 h post-infection, associated with formation of single and dense specks of the adapter molecule ASC in HSV(+) cells, but not in the neighboring bystander HSV(-) cells. This was associated with increased cleavages of Caspase-1, IL-1β, and IL-18. These findings suggest a previously unappreciated role of viral virulence in a synchronized early induction of the NLRP3, NLRP12, and IFI16 inflammasomes that lead to a damaging inflammatory response. A potential role of common virus virulent factors that stimulate this harmful inflammatory corneal disease is currently under investigation.

Innate Sensing of DNA Virus Genomes

DNA viruses are linked to many infectious diseases and contribute significantly to human morbidity and mortality worldwide. Moreover, DNA viral infections are usually lifelong and hard to eradicate. Under certain circumstances, these viruses can cause fatal disease, especially in children and immunocompromised patients. An efficient innate immune response against these viruses is critical, not only as the first line of host defense against viral infection but also for mounting more specific and robust adaptive immunity against the virus. Recognition of the viral DNA genome is the very first step of this whole process and is crucial for understanding viral pathogenesis as well as for preventing and treating DNA virus-associated diseases. This review focuses on the current state of our knowledge on how human DNA viruses are sensed by the host innate immune system and how viral proteins counteract this immune response.

Differential role of the NLRP3 inflammasome in infection and tumorigenesis

Dysregulated inflammation is one of the hallmarks of cancer initiation and progression. Emerging evidence indicates that inflammasomes play a central role in regulating immune cell functions in various infections and cancer. Inflammasomes are multimeric complexes consisting of nucleotide-binding oligomerization domain (NOD) -like receptors (NLRs). Among the NLRs, NOD1, NOD2 and NLRP3 respond to a variety of endogenous (i.e. damage-associated molecular patterns) and exogenous (i.e. pathogen-associated molecular patterns) stimuli. The NLRP3 inflammasome is associated with the onset and progression of autoinflammatory and autoimmune diseases, including metabolic disorders, multiple sclerosis, inflammatory bowel disease, and cryopyrin-associated periodic fever syndrome. NLRP3 is also associated with a wide variety of infections and tumorigenesis that are closely correlated with chemotherapy response and prognosis. In this review, we explore the rapidly expanding body of research on the expression and functions of NLRP3 in infections and cancers and outline novel inhibitors targeting the NLRP3 inflammasome that could be developed as therapeutic alternatives to current anticancer treatment.

Human Cytomegalovirus Immediate Early 86-kDa Protein Blocks Transcription and Induces Degradation of the Immature Interleukin-1β Protein during Virion-Mediated Activation of the AIM2 Inflammasome

Secretion of interleukin-1β (IL-1β) represents a fundamental innate immune response to microbial infection that, at the molecular level, occurs following activation of proteolytic caspases that cleave the immature protein into a secretable form. Human cytomegalovirus (HCMV) is the archetypal betaherpesvirus that is invariably capable of lifelong infection through the activity of numerous virally encoded immune evasion phenotypes. Innate immune pathways responsive to cytoplasmic double-stranded DNA (dsDNA) are known to be activated in response to contact between HCMV and host cells. Here, we used clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein 9 (Cas9) genome editing to demonstrate that the dsDNA receptor absent in melanoma 2 (AIM2) is required for secretion of IL-1β following HCMV infection. Furthermore, dsDNA-responsive innate signaling induced by HCMV infection that leads to activation of the type I interferon response is also shown, unexpectedly, to play a contributory role in IL-1β secretion. Importantly, we also show that rendering virus particles inactive by UV exposure leads to substantially increased IL-1β processing and secretion and that live HCMV can inhibit this, suggesting the virus encodes factors that confer an inhibitory effect on this response. Further examination revealed that ectopic expression of the immediate early (IE) 86-kDa protein (IE86) is actually associated with a block in transcription of the pro-IL-1β gene and, independently, diminishment of the immature protein. Overall, these results reveal two new and distinct phenotypes conferred by the HCMV IE86 protein, as well as an unusual circumstance in which a single herpesviral protein exhibits inhibitory effects on multiple molecular processes within the same innate immune response.IMPORTANCE Persistent infection with HCMV is associated with the operation of diverse evasion phenotypes directed at antiviral immunity. Obstruction of intrinsic and innate immune responses is typically conferred by viral proteins either associated with the viral particle or expressed immediately after entry. In line with this, numerous phenotypes are attributed to the HCMV IE86 protein that involve interference with innate immune processes via transcriptional and protein-directed mechanisms. We describe novel IE86-mediated phenotypes aimed at virus-induced secretion of IL-1β. Intriguingly, while many viruses target the function of the molecular scaffold required for IL-1β maturation to prevent this response, we find that HCMV and IE86 target the IL-1β protein specifically. Moreover, we show that IE86 impairs both the synthesis of the IL-1β transcript and the stability of the immature protein. This indicates an unusual phenomenon in which a single viral protein exhibits two molecularly separate evasion phenotypes directed at a single innate cytokine.

Infection and Functional Modulation of Human Monocytes and Macrophages by Varicella-Zoster Virus

Varicella-zoster virus (VZV) is associated with viremia during primary infection that is presumed to stem from infection of circulating immune cells. While VZV has been shown to be capable of infecting a number of different subsets of circulating immune cells, such as T cells, dendritic cells, and NK cells, less is known about the interaction between VZV and monocytes. Here, we demonstrate that blood-derived human monocytes are permissive to VZV replication in vitro VZV-infected monocytes exhibited each temporal class of VZV gene expression, as evidenced by immunofluorescent staining. VZV virions were observed on the cell surface and viral nucleocapsids were observed in the nucleus of VZV-infected monocytes by scanning electron microscopy. In addition, VZV-infected monocytes were able to transfer infectious virus to human fibroblasts. Infected monocytes displayed impaired dextran-mediated endocytosis, and cell surface immunophenotyping revealed the downregulation of CD14, HLA-DR, CD11b, and the macrophage colony-stimulating factor (M-CSF) receptor. Analysis of the impact of VZV infection on M-CSF-stimulated monocyte-to-macrophage differentiation demonstrated the loss of cell viability, indicating that VZV-infected monocytes were unable to differentiate into viable macrophages. In contrast, macrophages differentiated from monocytes prior to exposure to VZV were highly permissive to infection. This study defines the permissiveness of these myeloid cell types to productive VZV infection and identifies the functional impairment of VZV-infected monocytes.IMPORTANCE Primary VZV infection results in the widespread dissemination of the virus throughout the host. Viral transportation is known to be directly influenced by susceptible immune cells in the circulation. Moreover, infection of immune cells by VZV results in attenuation of the antiviral mechanisms used to control infection and limit spread. Here, we provide evidence that human monocytes, which are highly abundant in the circulation, are permissive to productive VZV infection. Furthermore, monocyte-derived macrophages were also highly permissive to VZV infection, although VZV-infected monocytes were unable to differentiate into macrophages. Exploring the relationships between VZV and permissive immune cells, such as human monocytes and macrophages, elucidates novel immune evasion strategies and provides further insight into the control that VZV has over the immune system.

Immunobiology of Varicella-Zoster Virus Infection

Varicella-zoster virus (VZV) causes clinically significant illness during acute and recurrent infection accompanied by robust innate and acquired immune responses. Innate immune cells in skin and ganglion secrete type I interferon (IFN-I) and proinflammatory cytokines to control VZV. Varicella-zoster virus subverts pattern recognition receptor sensing to modulate antigen presentation and IFN-I production. During primary infection, VZV hijacks T cells to disseminate to the skin and establishes latency in ganglia. Durable T- and B-cell memory formed within a few weeks of infection is boosted by reactivation or re-exposure. Antigen-specific T cells are recruited and potentially retained in VZV-infected skin to counteract reactivation. In latently VZV-infected ganglia, however, virus-specific T cells have not been recovered, suggesting that local innate immune responses control VZV latency. Antibodies prevent primary VZV infection, whereas T cells are fundamental to resolving disease, limiting severity, and preventing reactivation. In this study, we review current knowledge on the interactions between VZV and the human immune system.

Cytosolic Recognition of Microbes and Pathogens: Inflammasomes in Action

Infection is a dynamic biological process underpinned by a complex interplay between the pathogen and the host. Microbes from all domains of life, including bacteria, viruses, fungi, and protozoan parasites, have the capacity to cause infection. Infection is sensed by the host, which often leads to activation of the inflammasome, a cytosolic macromolecular signaling platform that mediates the release of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 and cleavage of the pore-forming protein gasdermin D, leading to pyroptosis. Host-mediated sensing of the infection occurs when pathogens inject or carry pathogen-associated molecular patterns (PAMPs) into the cytoplasm or induce damage that causes cytosolic liberation of danger-associated molecular patterns (DAMPs) in the host cell. Recognition of PAMPs and DAMPs by inflammasome sensors, including NLRP1, NLRP3, NLRC4, NAIP, AIM2, and Pyrin, initiates a cascade of events that culminate in inflammation and cell death. However, pathogens can deploy virulence factors capable of minimizing or evading host detection. This review presents a comprehensive overview of the mechanisms of microbe-induced activation of the inflammasome and the functional consequences of inflammasome activation in infectious diseases. We also explore the microbial strategies used in the evasion of inflammasome sensing at the host-microbe interaction interface.

Induction of plasmablasts by follicular helper T cell-CXCL13 axis upon occurrence of herpes zoster

Herpes zoster (HZ) is a recurrent varicella zoster virus (VZV) infection. Follicular helper T (Tfh) cells produce IL-21 and CXCL13, which contributes to the differentiation of plasmablasts. Plasmablasts are involved in the VZV-specific antibody production. We investigated the kinetics of circulating plasmablasts and circulating Tfh (cTfh) cells in 43 HZ patients. Plasma IL-21 and CXCL13 levels were also measured. We found an increase of circulating plasmablasts during the clinical course of HZ. The frequency of circulating plasmablasts positively correlated with VZV-specific IgG titers, frequency of activated cTfh cells, and plasma CXCL13 levels, but did not correlate with plasma IL-21 levels. In a representative case, the kinetics peaked in the order of cTfh cells, CXCL13, plasmablasts, and VZV IgG titer. These results suggest that cTfh-CXCL13 may have a crucial role in the differentiation of B cells into VZV-specific IgG-producing plasmablasts, resulting in boosting immunity against VZV reactivation.

Age-Associated Differences in Infection of Human Skin in the SCID Mouse Model of Varicella-Zoster Virus Pathogenesis

Varicella-zoster virus (VZV) is the skin-tropic human alphaherpesvirus responsible for both varicella-zoster and herpes zoster. Varicella-zoster and herpes zoster skin lesions have similar morphologies, but herpes zoster occurs disproportionally in older individuals and is often associated with a more extensive local rash and severe zoster-related neuralgia. We hypothesized that skin aging could also influence the outcome of the anterograde axonal transport of VZV to skin. We utilized human skin xenografts maintained in immunodeficient (SCID) mice to study VZV-induced skin pathology in vivo in fetal and adult skin xenografts. Here we found that VZV replication is enhanced in skin from older compared to younger adults, correlating with clinical observations. In addition to measures of VZV infection, we examined the expression of type I interferon (IFN) pathway components in adult skin and investigated elements of the cutaneous proliferative and inflammatory response to VZV infection in vivo Our results demonstrated that VZV infection of adult skin triggers intrinsic IFN-mediated responses such as we have described in VZV-infected fetal skin xenografts, including MxA as well as promyelocytic leukemia protein (PML), in skin cells surrounding lesions. Further, we observed that VZV elicited altered cell signaling and proliferative and inflammatory responses that are involved in wound healing, driven by follicular stem cells. These cellular changes are consistent with VZV-induced activation of STAT3 and suggest that VZV exploits the wound healing process to ensure efficient delivery of the virus to keratinocytes. Adult skin xenografts offer an approach to further investigate VZV-induced skin pathologies in vivoIMPORTANCE Varicella-zoster virus (VZV) is the agent responsible for both varicella-zoster and herpes zoster. Herpes zoster occurs disproportionally in older individuals and is often associated with a more extensive local rash and severe zoster-related neuralgia. To examine the effect of skin aging on VZV skin lesions, we utilized fetal and adult human skin xenografts maintained in immunodeficient (SCID) mice. We measured VZV-induced skin pathology, examined the expression of type I interferon (IFN) pathway components in adult skin, and investigated elements of the cutaneous proliferative and inflammatory response to VZV infection in vivo Our results demonstrate that characteristics of aging skin are preserved in xenografts; that VZV replication is enhanced in skin from older compared to younger adults, correlating with clinical observations; and that VZV infection elicits altered cell signaling and inflammatory responses. Adult skin xenografts offer an approach to further investigate VZV-induced skin pathologies in vivo.

Varicella zoster virus productively infects human natural killer cells and manipulates phenotype

Varicella zoster virus (VZV) is a ubiquitous human alphaherpesvirus, responsible for varicella upon primary infection and herpes zoster following reactivation from latency. To establish lifelong infection, VZV employs strategies to evade and manipulate the immune system to its advantage in disseminating virus. As innate lymphocytes, natural killer (NK) cells are part of the early immune response to infection, and have been implicated in controlling VZV infection in patients. Understanding of how VZV directly interacts with NK cells, however, has not been investigated in detail. In this study, we provide the first evidence that VZV is capable of infecting human NK cells from peripheral blood in vitro. VZV infection of NK cells is productive, supporting the full kinetic cascade of viral gene expression and producing new infectious virus which was transmitted to epithelial cells in culture. We determined by flow cytometry that NK cell infection with VZV was not only preferential for the mature CD56^dim NK cell subset, but also drove acquisition of the terminally-differentiated maturity marker CD57. Interpretation of high dimensional flow cytometry data with tSNE analysis revealed that culture of NK cells with VZV also induced a potent loss of expression of the low-affinity IgG Fc receptor CD16 on the cell surface. Notably, VZV infection of NK cells upregulated surface expression of chemokine receptors associated with trafficking to the skin –a crucial site in VZV disease where highly infectious lesions develop. We demonstrate that VZV actively manipulates the NK cell phenotype through productive infection, and propose a potential role for NK cells in VZV pathogenesis.

Varicella zoster virus (VZV) is a pervasive pathogen, causing chickenpox during primary infection and shingles when the virus reactivates from latency. VZV is therefore a lifelong infection for humans, warranting investigation of how this virus interacts with the immune system. One of the first immune cells to respond to viral infection are natural killer (NK) cells, yet little is known about how VZV interacts with NK cells. We demonstrate for the first time that VZV infects human blood NK cells and can use them to pass on infection to other cells in culture. Furthermore, VZV displays a predilection for infecting mature NK cells, and amplifies expression of receptors that would promote trafficking to the skin– the site of highly infectious lesions during chickenpox and shingles. Our findings suggest a role for NK cells in VZV disease and enhances our understanding of how lifelong infections interact with the human immune system.

Interleukin-1 Blockade: An Update on Emerging Indications

Interleukin (IL)-1 is a pro-inflammatory cytokine that induces local and systemic inflammation aimed to eliminate microorganisms and tissue damage. However, an increasing number of clinical conditions have been identified in which IL-1 production is considered inappropriate and IL-1 is part of the disease etiology. In autoinflammatory diseases, gout, Schnitzler's syndrome, and adult-onset Still's disease, high levels of inappropriate IL-1 production have been shown to be a key process in the etiology of the disease. In these conditions, blocking IL-1 has proven very effective in clinical studies. In other diseases, IL-1 has shown to be present in disease process but is not the central driving force of inflammation. In these conditions, including type 1 and 2 diabetes mellitus, acute coronary syndrome, amyotrophic lateral sclerosis, and several neoplastic diseases, the benefits of IL-1 blockade are minimal or absent.

Inflammasome Antagonism by Human Parainfluenza Virus Type 3 C Protein

Human parainfluenza virus type 3 (HPIV3) is a negative-sense single-stranded RNA virus belonging to the Paramyxoviridae family. HPIV3 is a lung-tropic virus causing airway diseases, including pneumonia, croup, and bronchiolitis, during infancy and childhood. The activation of the inflammasome by pathogens results in the production of proinflammatory cytokines such as interleukin-1β (IL-1β) during infection. Thus, the inflammasome-mediated proinflammatory response plays a critical role in regulating the immune response and virus clearance. The inflammasome is a multimeric protein complex triggering caspase-1 activation. Activated caspase-1 cleaves pro-IL-1β into its mature (and active) secretory form. Our study revealed inflammasome activation in macrophages following HPIV3 infection. Specifically, the activation of the NLRP3/ASC inflammasome resulted in the production of mature IL-1β from HPIV3-infected cells. Furthermore, Toll-like receptor 2 (TLR2) activation (first signal) and potassium efflux (second signal) constituted two cellular events mediating inflammasome activation following HPIV3 infection. During our studies, we surprisingly identified the HPIV3 C protein as an antagonist of inflammasome activation. The HPIV3 C protein is an accessory protein encoded by the open reading frame of the viral phosphoprotein (P) gene. The HPIV3 C protein interacted with the NLRP3 protein and blocked inflammasome activation by promoting the proteasomal degradation of the NLRP3 protein. Thus, our studies report NLRP3/ASC inflammasome activation by HPIV3 via TLR2 signaling and potassium efflux. Furthermore, we have identified HPIV3 C as a viral component involved in antagonizing inflammasome activation.IMPORTANCE Human parainfluenza virus type 3 (HPIV3) is a paramyxovirus that causes respiratory tract diseases during infancy and childhood. Currently, there is no effective vaccine or antiviral therapy for HPIV3. Therefore, in order to develop anti-HPIV3 agents (therapeutics and vaccines), it is important to study the HPIV3-host interaction during the immune response. Inflammasomes play an important role in the immune response. Inflammasome activation by HPIV3 has not been previously reported. Our studies demonstrated inflammasome activation by HPIV3 in macrophages. Specifically, HPIV3 activated the NLRP3/ASC inflammasome by TLR2 activation and potassium efflux. C proteins of paramyxoviruses are accessory proteins encoded by the viral phosphoprotein gene. The role of the C protein in inflammasome regulation was unknown. Surprisingly, our studies revealed that the HPIV3 C protein antagonizes inflammasome activation. In addition, we highlighted for the first time a mechanism utilized by paramyxovirus accessory proteins to block inflammasome activation. The HPIV3 C protein interacted with the NLRP3 protein to trigger the proteasomal degradation of the NLRP3 protein.

Inflammasome and Oral Diseases

One of the main steps in the development of the life in the earth is multicellularity. It enables cell differentiation and the development of morphological structures within an organism and is an essential factor in how to recognize friendly cells that are part of the multicellular organism and which foreign organisms can be harmful. Recognition includes devices such as the major histocompatibility complex (MHC), and the pattern recognition receptors (PRRs). PRRs are a group of proteins expressed by cells of the innate immune system that identify two classes of products: pathogen-associated molecular patterns (PAMPs), related to microbial pathogens, and damage-associated molecular patterns (DAMPs), associated with cell components that are released during cell damage or death. All these activate the inflammasome, which is a multiprotein oligomer that includes caspase 1, PYCARD, NALP, and caspase 5 (also known as caspase 11 or ICH-3). It is responsible for activation of inflammatory processes and has been shown to induce cell pyroptosis, a programmed cell death distinct from apoptosis, and promotes the maturation of the inflammatory cytokines interleukin 1β (IL-1β) and interleukin 18 (IL-18). We review whether inflammasome is related to diseases that can occur in the oral cavity. The mouth is always a possible environment for the development of pathological conditions because of the wide variety of microorganisms. Small variations in the equilibrium of the oral flora can cause disorders that could affect the organism in a systemic form. We provide data on periodontal disease, candidiasis, herpes virus, oral cancer, caries, and other oral diseases. There are very few papers that study this issue; therefore, we need more investigation and publications about inflammatory molecular processes, and more specifically, related to the inflammasome complex.

Inflammasomes and its importance in viral infections

A complex interplay between pathogen and host determines the immune response during viral infection. A set of cytosolic sensors are expressed by immune cells to detect viral infection. NOD-like receptors (NLRs) comprise a large family of intracellular pattern recognition receptors. Members of the NLR family assemble into large multiprotein complexes, termed inflammasomes, which induce downstream immune responses to specific pathogens, environmental stimuli, and host cell damage. Inflammasomes are composed of cytoplasmic sensor molecules such as NLRP3 or absent in melanoma 2 (AIM2), the adaptor protein ASC (apoptosis-associated speck-like protein containing caspase recruitment domain), and the effector protein procaspase-1. The inflammasome operates as a platform for caspase-1 activation, resulting in caspase-1-dependent proteolytic maturation and secretion of interleukin (IL)-1β and IL-18. This, in turn, activates the expression of other immune genes and facilitates lymphocyte recruitment to the site of primary infection, thereby controlling invading pathogens. Moreover, inflammasomes counter viral replication and remove infected immune cells through an inflammatory cell death, program termed as pyroptosis. As a countermeasure, viral pathogens have evolved virulence factors to antagonise inflammasome pathways. In this review, we discuss the role of inflammasomes in sensing viral infection as well as the evasion strategies that viruses have developed to evade inflammasome-dependent immune responses. This information summarises our understanding of host defence mechanisms against viruses and highlights research areas that can provide new approaches to interfere in the pathogenesis of viral diseases.

Evolutionary adaptation revealed by comparative genome analysis of woolly mammoths and elephants

Comparative genomics studies typically limit their focus to single nucleotide variants (SNVs) and that was the case for previous comparisons of woolly mammoth genomes. We extended the analysis to systematically identify not only SNVs but also larger structural variants (SVs) and indels and found multiple mammoth-specific deletions and duplications affecting exons or even complete genes. The most prominent SV found was an amplification of RNase L (with different copy numbers in different mammoth genomes, up to 9-fold), involved in antiviral defense and inflammasome function. This amplification was accompanied by mutations affecting several domains of the protein including the active site and produced different sets of RNase L paralogs in four mammoth genomes likely contributing to adaptations to environmental threats. In addition to immunity and defense, we found many other unique genetic changes in woolly mammoths that suggest adaptations to life in harsh Arctic conditions, including variants involving lipid metabolism, circadian rhythms, and skeletal and body features. Together, these variants paint a complex picture of evolution of the mammoth species and may be relevant in the studies of their population history and extinction.

Inflammasomes and dermatology

Inflammasomes are intracellular multiprotein complexes that comprise part of the innate immune response. Since their definition, inflammasome disorders have been linked to an increasing number of diseases. Autoinflammatory diseases refer to disorders in which local factors lead to the activation of innate immune cells, causing tissue damage when in the absence of autoantigens and autoantibodies. Skin symptoms include the main features of monogenic inflammasomopathies, such as Cryopyrin-Associated Periodic Syndromes (CAPS), Familial Mediterranean Fever (FMF), Schnitzler Syndrome, Hyper-IgD Syndrome (HIDS), PAPA Syndrome, and Deficiency of IL-1 Receptor Antagonist (DIRA). Concepts from other pathologies have also been reviewed in recent years, such as psoriasis, after the recognition of a combined contribution of innate and adaptive immunity in its pathogenesis. Inflammasomes are also involved in the response to various infections, malignancies, such as melanoma, autoimmune diseases, including vitiligo and lupus erythematosus, atopic and contact dermatitis, acne, hidradenitis suppurativa, among others. Inhibition of the inflammasome pathway may be a target for future therapies, as already occurs in the handling of CAPS, through the introduction of IL-1 inhibitors. This study presents a literature review focusing on the participation of inflammasomes in skin diseases.

Epstein-Barr virus infection-induced inflammasome activation in human monocytes

Inflammasomes are cytoplasmic sensors that regulate the activity of caspase-1 and the secretion of interleukin-1β (IL-1β) or interleukin-18 (IL-18) in response to foreign molecules, including viral pathogens. They are considered to be an important link between the innate and adaptive immune responses. However, the mechanism by which inflammasome activation occurs during primary Epstein-Barr virus (EBV) infection remains unknown. Human B lymphocytes and epithelial cells are major targets of EBV, although it can also infect a variety of other cell types. In this study, we found that EBV could infect primary human monocytes and the monocyte cell line, THP-1, inducing inflammasome activation. We incubated cell-free EBV with THP-1 cells or primary human monocytes, then confirmed EBV infection using confocal microscopy and flow cytometry. Lytic and latent EBV genes were detected by real-time RT-PCR in EBV-infected monocytes. EBV infection of THP-1 cells and primary human monocytes induced caspase-dependent IL-1β production, while EBV infection of B-cell or T-cell lines did not induce IL-1β production. To identify the sensor molecule responsible for inflammasome activation during EBV infection, we examined the mRNA and the protein levels of NLR family pyrin domain-containing 3 (NLRP3), absent in melanoma 2 (AIM2), and interferon-inducible protein 16 (IFI16). Increased AIM2 levels were observed in EBV-infected THP-1 cells and primary human monocytes, whereas levels of IFI16 and NLRP3 did not show remarkable change. Furthermore, knockdown of AIM2 by small interfering RNA attenuated caspase-1 activation. Taken together, our results suggest that EBV infection of human monocytes induces caspase-1-dependent IL-1β production, and that AIM2, acting as an inflammasome, is involved in this response.

Varicella-Zoster Virus Activates CREB, and Inhibition of the pCREB-p300/CBP Interaction Inhibits Viral Replication In Vitro and Skin Pathogenesis In Vivo

Varicella-zoster virus (VZV) is an alphaherpesvirus that causes varicella upon primary infection and zoster upon reactivation from latency in sensory ganglion neurons. The replication of herpesviruses requires manipulation of cell signaling pathways. Notably, CREB, a factor involved in the regulation of several cellular processes, is activated upon infection of T cells with VZV. Here, we report that VZV infection also induced CREB phosphorylation in fibroblasts and that XX-650-23, a newly identified inhibitor of the phosphorylated-CREB (pCREB) interaction with p300/CBP, restricted cell-cell spread of VZV in vitro CREB phosphorylation did not require the viral open reading frame 47 (ORF47) and ORF66 kinases encoded by VZV. Evaluating the biological relevance of these observations during VZV infection of human skin xenografts in the SCID mouse model of VZV pathogenesis showed both that pCREB was upregulated in infected skin and that treatment with XX-650-23 reduced infectious-virus production and limited lesion formation compared to treatment with a vehicle control. Thus, processes of CREB activation and p300/CBP binding are important for VZV skin infection and may be targeted for antiviral drug development.

IMPORTANCE

Varicella-zoster virus (VZV) is a common pathogen that causes chicken pox and shingles. As with all herpesviruses, the infection is acquired for life, and the virus can periodically reactivate from latency. Although VZV infection is usually benign with few or no deleterious consequences, infection can be life threatening in immunocompromised patients. Otherwise healthy elderly individuals who develop zoster as a consequence of viral reactivation are at risk for postherpetic neuralgia (PHN), a painful and long-lasting complication. Current vaccines use a live attenuated virus that is usually safe but cannot be given to many immunodeficient patients and retains the capacity to establish latency and reactivate, causing zoster. Antiviral drugs are effective against severe VZV infections but have little impact on PHN. A better understanding of virus-host cell interactions is relevant for developing improved therapies to safely interfere with cellular processes that are crucial for VZV pathogenesis.

Mitochondria and Antiviral Immunity

Mitochondria are unique dynamic organelles that evolved from free-living bacteria into endosymbionts of mammalian hosts (Sagan 1967; Hatefi 1985). They have a distinct ~16.6 kb closed circular DNA genome coding for 13 polypeptides (Taanman 1999). In addition, a majority of the ~1500 mitochondrial proteins are encoded in the nucleus and transported to the mitochondria (Bonawitz et al. 2006). Mitochondria have two membranes: an outer smooth membrane and a highly folded inner membrane called cristae, which encompasses the matrix that houses the enzymes of the tricarboxylic acid (TCA) cycle and lipid metabolism. The inner mitochondrial membrane houses the protein complexes comprising the electron transport chain (ETC) (Hatefi 1985).

Immune response and reactogenicity of intradermal administration versus subcutaneous administration of varicella-zoster virus vaccine: an exploratory, randomised, partly blinded trial

BACKGROUND

The licensed live, attenuated varicella-zoster virus vaccine prevents herpes zoster in adults older than 50 years. We aimed to determine whether intradermal administration of zoster vaccine could enhance vaccine immunogenicity compared with conventional needle subcutaneous administration.

METHODS

In this randomised, dose-ranging study, adults aged 50 years or older who had a history of varicella or who had resided in a country with endemic varicella-zoster virus infection for 30 years or more were eligible. Participants received the approved full or a 1/3 dose of zoster vaccine given subcutaneously or one of four intradermal doses (full, 1/3, 1/10, or 1/27 dose) using the MicronJet600 device. The two subcutaneous doses and the four intradermal doses were randomised (1·5:1:1:1:1:1) by computer generated sequence with randomisation stratified by age (50-59 years or 60 years or older). The primary immunogenicity endpoint was the change from baseline in IgG antibody to varicella-zoster virus-specific glycoproteins (gpELISA) measured at 6 weeks. All patients were included in the primary and safety analyses. This study is registered with ClinicalTrials.gov, number NCT01385566.

FINDINGS

Between Sept 2, 2011, and Jan 13, 2012, 224 participants were enrolled from three clinics in the USA and 223 were randomly assigned: 52 to receive the full dose subcutaneous zoster vaccine, 34 to receive the 1/3 dose subcutaneous zoster vaccine, 34 to receive the full dose intradermal zoster vaccine, 35 to receive the 1/3 dose intradermal zoster vaccine, 34 to receive the 1/10 dose intradermal zoster vaccine, and 34 to receive the 1/27 dose intradermal zoster vaccine. Full dose zoster vaccine given subcutaneously resulted in a gpELISA geometric mean fold-rise (GMFR) of 1·74 (90% CI 1·48-2·04) at 6 weeks post-vaccination compared with intradermal administration which resulted in a significantly higher gpELISA GMFR of 3·25 (2·68-3·94; p<0·0001), which also remained high at 18 months. An apparent dose-response relation was observed with intradermal administration (1/3 dose subcutaneous GMFR 1·64 [90% CI 1·36-1·99], 1/3 dose intradermal 2·58 (2·13-3·13), 1/10 dose intradermal 2·22 [1·83-2·69], and 1/27 dose intradermal 1·64 [1·35-2·00]). Each partial dose of zoster vaccine given intradermaly had a gpELISA GMFR comparable to that of full dose zoster vaccine given subcutaneously. Transient erythema and induration were more common after intradermal administration (31% erythema for full subcutaneous dose and 77% for intradermal dose).

INTERPRETATION

Intradermal zoster vaccine showed a greater increase in varicella-zoster virus gpELISA antibody compared with subcutaneous zoster vaccine at comparable doses. Larger and longer studies of intradermal administration of live, attenuated zoster vaccine are needed to provide convincing evidence of improved cell mediated immunity.

FUNDING

Merck & Co Inc.

HIV Promotes NLRP3 Inflammasome Complex Activation in Murine HIV-Associated Nephropathy

Dysregulated growth and loss of podocytes are important features of HIV-associated nephropathy. Recently, HIV was reported to induce a new type of programed cell death, pyroptosis, in T lymphocytes through induction of Nod-like receptor protein 3 (NLRP3) inflammasome complexes. We evaluated the role of HIV in podocyte NLRP3 inflammasome formation both in vivo and in vitro. Renal cortical sections of HIV-transgenic mice (Tg26) displayed increased expression of NLRP3, ASC (a CARD protein), caspase-1, and IL-1β proteins, confirming NLRP3 inflammasome complex formation in podocytes of Tg26 mice. Renal tissues of Tg26 mice also displayed enhanced mRNA levels and protein expressions of inflammasome markers (NLRP3, ASC, and caspase-1, and IL-1β). Serum of Tg26 mice also showed elevated concentrations of IL-1β cytokine compared with FVBN mice. HIV induced pyroptosis in a dose- and time-dependent manner within podocytes, a phenotype of inflammasome activation. Caspase-1 inhibitor not only attenuated podocyte expression of caspase-1 and IL-1β but also provided protection against pyroptosis, suggesting that HIV-induced podocyte injury was mediated by caspase-1 activation. Interestingly, HIV-induced podocyte pyroptosis could be partially inhibited by Tempol (a superoxide dismutase-mimetic agent) and by glyburide (an inhibitor of potassium efflux). These findings suggest that generation of reactive oxygen species and potassium efflux contribute to HIV-induced pyroptosis and NLRP3 inflammasome activation in podocytes.

Suppressor of Cytokine Signaling 3 Expression Induced by Varicella-Zoster Virus Infection Results in the Modulation of Virus Replication

Varicella-zoster virus (VZV) is an important viral pathogen that is responsible for causing varicella (chickenpox) and herpes zoster (shingles). VZV has been shown to suppress early anti-viral innate immune responses, but the exact mechanisms are not yet well understood. Here we demonstrate that host control of VZV is impaired by the expression of suppressor of cytokine signaling (SOCS)3. We used three different cell types to characterize VZV-induced anti-viral and inflammatory responses. Infection of human fibroblasts (MRC-5) and human macrophages (THP-1) with VZV triggered upregulation of anti-viral responsive gene expression (IFN-α, IFN-β) in the early phases of infection, followed by the waning of these IFNs in the late phases of infection. Conversely, VZV infection in keratinocytes (HaCaT) resulted in a persistent increase in type I IFN gene expression. Interestingly, increase in SOCS1 and 3 expressions coincided with a reduction in phosphorylation of the signal transducer and activator of transcription protein 3 (STAT3) in VZV-infected MRC-5 cells. Furthermore, VZV infection increased the production of pro-inflammatory cytokines, including interleukin (IL)-6, -8, and IFN-γ-inducible protein 10 (IP-10). Knockdown of SOCS3 inhibited viral replication and enhanced secretion levels of IL-6, whereas overexpression of SOCS3 did not affect viral replication efficiency and host response. In conclusion, our data suggest that VZV infection induces SOCS3 expression, resulting in modulation of type I IFN signaling and viral replication.

The emerging role of nuclear viral DNA sensors

Detecting pathogenic DNA by intracellular receptors termed "sensors" is critical toward galvanizing host immune responses and eliminating microbial infections. Emerging evidence has challenged the dogma that sensing of viral DNA occurs exclusively in sub-cellular compartments normally devoid of cellular DNA. The interferon-inducible protein IFI16 was shown to bind nuclear viral DNA and initiate immune signaling, culminating in antiviral cytokine secretion. Here, we review the newly characterized nucleus-originating immune signaling pathways, their links to other crucial host defenses, and unique mechanisms by which viruses suppress their functions. We frame these findings in the context of human pathologies associated with nuclear replicating DNA viruses.

NLRP3 inflammasome is responsible for Hantavirus inducing interleukin-1β in THP-1 cells

Persistent high fever is one typical clinical symptom of hemorrhagic fever with renal syndrome (HFRS) and circulating interleukin-1β (IL-1β) is elevated throughout HFRS. The mechanisms responsible for viral induction of IL-1β secretion are unknown. In the present study, Hantaan virus (HTNV) induced the secretion of IL-1β in the human monocytic cell line THP-1. Induction of IL-1β by HTNV relies on the activation of caspase-1. Small hairpin RNA knockdown in HTNV-infected THP-1 cells indicated that nucleotide-binding domain, leucine-rich repeat containing protein 3 (NLRP3) recruits the adaptor apoptosis-associated speck-like protein and caspase-1 to form an NLRP3 inflammasome complex, crucial for the induction of IL-1β. In HTNV-infected THP-1 cells, reactive oxygen species release, but not extracellular adenosine triphosphate, was crucial for IL-1β production. In conclusion, Hantavirus induces the formation of the NLRP3 inflammasome in THP-1 cells and this may be responsible for the elevated IL-1β levels in HFRS patients.

RNase L activates the NLRP3 inflammasome during viral infections

The NLRP3 inflammasome assembles in response to danger signals, triggering self-cleavage of procaspase-1 and production of the proinflammatory cytokine IL-1β. Although virus infection activates the NLRP3 inflammasome, the underlying events remain incompletely understood. We report that virus activation of the NLRP3 inflammasome involves the 2',5'-oligoadenylate (2-5A) synthetase(OAS)/RNase L system, a component of the interferon-induced antiviral response that senses double-stranded RNA and activates endoribonuclease RNase L to cleave viral and cellular RNAs. The absence of RNase L reduces IL-1β production in influenza A virus-infected mice. RNA cleavage products generated by RNase L enhance IL-1β production but require the presence of 2',3'-cyclic phosphorylated termini characteristic of RNase L activity. Additionally, these cleavage products stimulate NLRP3 complex formation with the DExD/H-box helicase, DHX33, and mitochondrial adaptor protein, MAVS, which are each required for effective NLRP3 inflammasome activation. Thus, RNA cleavage events catalyzed by RNase L are required for optimal inflammasome activation during viral infections.